To provide an agitating device for hot water in a boiler of such type as to reheat the hot water by using steam or agitate it by injecting steam thereinto, designed to be usable through the changeover between steam to be injected into the hot water for agitation and air fairly lower in temperature than the steam.

This agitating device for the hot water in a boiler of such type that the inside of a hot water bath is divided with a partition wall to form an endless hot water flow channel, and a dried small fish material for getting broth charged into the flow channel is boiled up during allowing it to flow concomitantly with the hot water, is so designed that an air jet tube for agitating the hot water is laid along the bottom surface of the hot water flow channel and provided with a number of nozzles opened toward the bottom surface and also a valve means is furnished to selectively connect the air jet tube to a steam source or an air source.